Re: [PATCH v5 4/6] KVM: arm64: Provide invalidate_icache_range at non-VHE EL2

[wangyanan (Y)]

Hi Marc,

On 2021/6/2 18:22, Marc Zyngier wrote:
> On Thu, 15 Apr 2021 12:50:30 +0100,
> Yanan Wang <wangyanan55@xxxxxxxxxx> wrote:
> > We want to move I-cache maintenance for the guest to the stage-2
> > page table code for performance improvement. Before it can work,
> > we should first make function invalidate_icache_range available
> > to non-VHE EL2 to avoid compiling or program running error, as
> > pgtable.c is now linked into the non-VHE EL2 code for pKVM mode.
> >
> > In this patch, we only introduce symbol of invalidate_icache_range
> > with no real functionality in nvhe/cache.S, because there haven't
> > been situations found currently where I-cache maintenance is also
> > needed in non-VHE EL2 for pKVM mode.
> >
> > Signed-off-by: Yanan Wang <wangyanan55@xxxxxxxxxx>
> > ---
> >   arch/arm64/kvm/hyp/nvhe/cache.S | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/arch/arm64/kvm/hyp/nvhe/cache.S b/arch/arm64/kvm/hyp/nvhe/cache.S
> > index 36cef6915428..a125ec9aeed2 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/cache.S
> > +++ b/arch/arm64/kvm/hyp/nvhe/cache.S
> > @@ -11,3 +11,14 @@ SYM_FUNC_START_PI(__flush_dcache_area)
> >   	dcache_by_line_op civac, sy, x0, x1, x2, x3
> >   	ret
> >   SYM_FUNC_END_PI(__flush_dcache_area)
> > +
> > +/*
> > + *	invalidate_icache_range(start,end)
> > + *
> > + *	Ensure that the I cache is invalid within specified region.
> > + *
> > + *	- start   - virtual start address of region
> > + *	- end     - virtual end address of region
> > + */
> > +SYM_FUNC_START(invalidate_icache_range)
> > +SYM_FUNC_END(invalidate_icache_range)
> This is a good indication that something is really wrong.
>
> If you were to provide cache management callbacks as part of the
> mm_ops themselves (or a similar abstraction), you wouldn't have to do
> these things.
Yes, we definitely don't need this work if we do that.

Thanks,
Yanan
> 	M.